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authorThomas Gleixner <tglx@linutronix.de>2015-05-26 22:50:24 +0000
committerThomas Gleixner <tglx@linutronix.de>2015-06-19 15:18:27 +0200
commit3bb475a3446facd0425d3f2fe7e85bf03c5c6c05 (patch)
tree0b7af9596cdac5bb89bd2f3ad70e0f26a615b706 /kernel/time/timer.c
parent887d9dc989eb0154492e41e7c07492edbb088ba1 (diff)
downloadlinux-sh-3bb475a3446facd0425d3f2fe7e85bf03c5c6c05.tar.gz
timers: Sanitize catchup_timer_jiffies() usage
catchup_timer_jiffies() has been applied blindly to several functions without looking for possible better ways to do it. 1) internal_add_timer() Move the update to base->all_timers before we actually insert the timer into the wheel. 2) detach_if_pending() Again the update to base->all_timers allows us to explicitely do the timer_jiffies update in place, if this was the last timer which got removed. 3) __run_timers() We only check on entry, which is silly, because base->timer_jiffies can be behind - especially on NOHZ kernels - and if there is a single deferrable timer somewhere between base->timer_jiffies and jiffies we expire it and then loop until base->timer_jiffies == jiffies. Move it into the loop. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Paul McKenney <paulmck@linux.vnet.ibm.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Eric Dumazet <edumazet@google.com> Cc: Viresh Kumar <viresh.kumar@linaro.org> Cc: John Stultz <john.stultz@linaro.org> Cc: Joonwoo Park <joonwoop@codeaurora.org> Cc: Wenbo Wang <wenbo.wang@memblaze.com> Link: http://lkml.kernel.org/r/20150526224511.662994644@linutronix.de Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'kernel/time/timer.c')
-rw-r--r--kernel/time/timer.c40
1 files changed, 16 insertions, 24 deletions
diff --git a/kernel/time/timer.c b/kernel/time/timer.c
index 7775d454a204..d5e017970ac7 100644
--- a/kernel/time/timer.c
+++ b/kernel/time/timer.c
@@ -351,20 +351,6 @@ void set_timer_slack(struct timer_list *timer, int slack_hz)
}
EXPORT_SYMBOL_GPL(set_timer_slack);
-/*
- * If the list is empty, catch up ->timer_jiffies to the current time.
- * The caller must hold the tvec_base lock. Returns true if the list
- * was empty and therefore ->timer_jiffies was updated.
- */
-static bool catchup_timer_jiffies(struct tvec_base *base)
-{
- if (!base->all_timers) {
- base->timer_jiffies = jiffies;
- return true;
- }
- return false;
-}
-
static void
__internal_add_timer(struct tvec_base *base, struct timer_list *timer)
{
@@ -411,7 +397,10 @@ __internal_add_timer(struct tvec_base *base, struct timer_list *timer)
static void internal_add_timer(struct tvec_base *base, struct timer_list *timer)
{
- (void)catchup_timer_jiffies(base);
+ /* Advance base->jiffies, if the base is empty */
+ if (!base->all_timers++)
+ base->timer_jiffies = jiffies;
+
__internal_add_timer(base, timer);
/*
* Update base->active_timers and base->next_timer
@@ -421,7 +410,6 @@ static void internal_add_timer(struct tvec_base *base, struct timer_list *timer)
time_before(timer->expires, base->next_timer))
base->next_timer = timer->expires;
}
- base->all_timers++;
/*
* Check whether the other CPU is in dynticks mode and needs
@@ -718,7 +706,6 @@ detach_expired_timer(struct timer_list *timer, struct tvec_base *base)
if (!tbase_get_deferrable(timer->base))
base->active_timers--;
base->all_timers--;
- (void)catchup_timer_jiffies(base);
}
static int detach_if_pending(struct timer_list *timer, struct tvec_base *base,
@@ -733,8 +720,9 @@ static int detach_if_pending(struct timer_list *timer, struct tvec_base *base,
if (timer->expires == base->next_timer)
base->next_timer = base->timer_jiffies;
}
- base->all_timers--;
- (void)catchup_timer_jiffies(base);
+ /* If this was the last timer, advance base->jiffies */
+ if (!--base->all_timers)
+ base->timer_jiffies = jiffies;
return 1;
}
@@ -1184,14 +1172,18 @@ static inline void __run_timers(struct tvec_base *base)
struct timer_list *timer;
spin_lock_irq(&base->lock);
- if (catchup_timer_jiffies(base)) {
- spin_unlock_irq(&base->lock);
- return;
- }
+
while (time_after_eq(jiffies, base->timer_jiffies)) {
struct list_head work_list;
struct list_head *head = &work_list;
- int index = base->timer_jiffies & TVR_MASK;
+ int index;
+
+ if (!base->all_timers) {
+ base->timer_jiffies = jiffies;
+ break;
+ }
+
+ index = base->timer_jiffies & TVR_MASK;
/*
* Cascade timers: